Control apparatus and control method for direct injection spark ignition internal combustion engine

Abstract

An ECU controls an internal combustion engine that creates a tumble flow in each engine cylinder and intensifies the tumble flow using fuel injected at a timing near the intake stroke bottom dead center during homogeneous combustion. The ECU includes a fuel property identifying mechanism identifying the property of fuel and combustion state changing mechanism changing the combustion state. When the fuel has a property that requires a stoichiometric air-fuel ratio lower than the stoichiometric air-fuel ratio for gasoline, the combustion state changing mechanism changes the combustion state by, for example, retarding the ignition timing, so that the combustion progresses moderately. This prevents an excessive increase in the combustion speed.

1. A control apparatus in a direct injection spark ignition internal combustion engine including an engine cylinder comprising:
 a fuel property identifying device that identifies a property of a fuel that is injected into the engine cylinder; and 
 a combustion state changing device that changes a combustion state based on the property of the fuel, 
 wherein the control apparatus creates a tumble flow in the engine cylinder and intensifies the tumble flow by injecting the fuel at a timing near an intake stroke bottom dead center during homogenous combustion, 
 wherein the fuel property identifying device identifies the property of the fuel by detecting an alcohol concentration in the fuel, 
 wherein the combustion state changing device changes a degree to which the tumble flow is intensified based on the property of the fuel by reducing a thrust force of the fuel as the alcohol concentration detected by the fuel property identifying device increases. 
 
     
     
       2. The control apparatus according to  claim 1 , wherein the combustion state changing device reduces the thrust force of the fuel by changing an injection pressure of the fuel. 
     
     
       3. The control apparatus according to  claim 1 , wherein the combustion state changing device changes the tumble flow intensification degree by changing the injection timing of the fuel. 
     
     
       4. The control apparatus according to  claim 1 , wherein the combustion state changing device changes the tumble flow intensification degree by changing the injection direction of the fuel. 
     
     
       5. The control apparatus according to  claim 4 , further comprising a fuel injection valve including at least two injection holes having different injection directions, wherein:
 the combustion state changing device changes the injection direction of the fuel by switching from one of the injection holes to the other of the injection holes. 
 
     
     
       6. The control apparatus according to  claim 3 , wherein:
 the fuel property identifying device detects the property of the fuel by detecting the concentration of alcohol in the fuel; and 
 the combustion state changing device shifts the injection timing of the fuel farther away from near the intake stroke bottom dead center as the alcohol concentration detected by the fuel property identifying device increases. 
 
     
     
       7. The control apparatus according to  claim 6 , wherein the combustion state changing device shifts the injection timing of the fuel away from near the intake stroke bottom dead center by advancing the injection timing from the intake stroke bottom dead center. 
     
     
       8. The control apparatus according to  claim 1 , wherein the fuel property identifying device is an alcohol concentration sensor that detects the alcohol concentration in the fuel. 
     
     
       9. A method for controlling a direct injection spark ignition internal combustion engine that creates a tumble flow in an engine cylinder and intensifies the tumble flow using fuel injected at a timing near an intake stroke bottom dead center during homogenous combustion, comprising:
 identifying an alcohol concentration in the fuel as a property of the fuel; and 
 changing a combustion state based on the property of the fuel identified, 
 wherein a degree to which the tumble flow is intensified by the fuel, is changed by reducing a thrust force of the fuel as the alcohol concentration of the fuel that is identified increases. 
 
     
     
       10. The method for controlling the direct injection spark ignition internal combustion engine of  claim 9 , wherein the thrust force of the fuel is reduced by changing an injection pressure of the fuel.